Tighten it up will eliminate all the play and after that it will start to put a preload on the bearings,tighten it til you get the preload your looking for, I tighten up a little then check it with an inch pound torque wrench,tighten some more, then spin it over a couple of times then just fiddle with it ,check it with torq. wrench for your specs. Golden rule : If you get the pinion preload right and the backlash right and side bearing preload right its GOT to have the correct pattern on the gears!!! NEVER FAILS !!!! DR. Ive done a lot of rears over the yrs!